Water softener sizing - what do I need?

Building a new house, bought a Hach hardness and iron test kit. No iron detected in the water, hardness shows 8 gpg. The house has 3 full baths, right now it's just my wife and I, but will have guests visiting every once in a while, and a kid in the next year or two. I've tried reading and understanding the various sizing web sites, but am not sure what size I need. I've read that most companies size based on "size" versus cu ft of resin. Others say that I need to calculate my SFR, and go from there - but doesn't give any method to calculate the SFR. I'd like to get a Fleck 7000 series, as I think this will fit the bill for the size of our house, but not sure of how much resin / size I need. Can anyone help?

The SFR is important if you are going to run ALL your faucets at the same time. When I say ALL, I mean every single water connection in the house. Most folks don't do this but may have a shower, washer and the dish washer going at the same time. So to size your unit, I would go by the days between regens. A 1 CF system set using the best salt efficiency will yield 20K @ 6 lbs of salt. So 20K/8GPG/2PPL/65Avg usage=19 days between regen. With a 1 day reserve, you will regen every 18 days. This is not bad unless the iron content is high which you said was not showing up. I take it that you are on well water?

And a 1.0 cuft has a constant SFR of 9 gpm and when that is exceeded, the resin will not get your hardness down to 0 gpg. IOWs you get some hardness through the softener. IMO that's like buying a vehicle that won't start a couple times a week. Most shower heads are 2.5 gpm, faucets 2.0-2.5 gpm, washing machines 3-3.5 gpm, toilets 1-1.5 gpm.

The SFR is important if you are going to run ALL your faucets at the same time. When I say ALL, I mean every single water connection in the house. Most folks don't do this but may have a shower, washer and the dish washer going at the same time. So to size your unit, I would go by the days between regens. A 1 CF system set using the best salt efficiency will yield 20K @ 6 lbs of salt. So 20K/8GPG/2PPL/65Avg usage=19 days between regen. With a 1 day reserve, you will regen every 18 days. This is not bad unless the iron content is high which you said was not showing up. I take it that you are on well water?

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Thanks for the reply! I'm actually on city water (Florida). With regards to the regen - is there any way to set the regen to once a week? I know that it would be less efficient since wouldn't be using the entire capacity of the 1 cu ft of resin. Would it cause any harm to do this? I've read that if you wait too long to regen, the resin could get channeling or have other issues.

And a 1.0 cuft has a constant SFR of 9 gpm and when that is exceeded, the resin will not get your hardness down to 0 gpg. IOWs you get some hardness through the softener. IMO that's like buying a vehicle that won't start a couple times a week. Most shower heads are 2.5 gpm, faucets 2.0-2.5 gpm, washing machines 3-3.5 gpm, toilets 1-1.5 gpm.

Click on the "Click Here" in Gary's signature. Follow that as best you can. Then click the link at the bottom of that page that will get you to a special calculator.

You are unlikely to open every faucet at the same time. Having some hardness get by occasionally is not so bad. I expect that you have neighbors that have no softener at all.

Most controllers allow you to set up a regeneration every week (although mine is not one of them). Many allow you to regenerate when you have used up enough capacity that you may exceed capacity by waiting a day, but set a maximum time between recharges that will occur even if you have not used any softened water at all.

If you use the entire capacity, which means you must set the salt dose at 15 lbs per cuft of resin you get 2000 grains of softening per lb of salt used, that's 30K in a 1.0 cuft (30,000 divided by 15= 2000). Compared to setting the salt dose to 6 lbs and getting 20K which is 3333 grains of softening per cuft of resin. That's an increase in salt efficiency of 1333 grains per lb. for every regeneration. I.E. if you went to a 1.5 cuft, at 6 lbs/cuft which is 9 lbs, you regenerate 30K where with a 1.0 cuft you need 15 lbs, or 6 more lbs for the same 30K of capacity. Plus, you never want to use all the capacity or you have to use 15 lbs per cuft to get all the resin regenerated again. It's like waiting to buy gas until you run out, it is not good to do that and can cause engine damage.

Can you tell me how you got .75 ft out of what I said about SFR?

Let's say you have 2 showers running (5gpm) and a toilet is flushed (1.5gpm) and someone starts the laundry washer (3.5gpm), your peak demand is the total of whatever is running so 10 gpm in my example. You would overrun the 1.0 cuft 9 gpm and not get all the hardness out of the water. And I'd be telling you that you should have bought a 1.5 cuft (12 gpm SFR) and set the capacity to the same as the 1.0 cuft and the salt to whatever lbs at 3333 grains per lb.. 2*60gals/day/person= 120* 8= 960* 8 days = 8640 rounded to 9K. That would be 1125 gals minus one day of 120 gals for the reserve with a meter setting of 1000 gals. 9000/ 3333= 3 lbs of salt per regeneration and that gets you a regeneration on average every 8 days with a constant SFR of 12 gpm. Then if you have a child, redo the math with 3 people at 60 gals per person etc..

If you use the entire capacity, which means you must set the salt dose at 15 lbs per cuft of resin you get 2000 grains of softening per lb of salt used, that's 30K in a 1.0 cuft (30,000 divided by 15= 2000). Compared to setting the salt dose to 6 lbs and getting 20K which is 3333 grains of softening per cuft of resin. That's an increase in salt efficiency of 1333 grains per lb. for every regeneration. I.E. if you went to a 1.5 cuft, at 6 lbs/cuft which is 9 lbs, you regenerate 30K where with a 1.0 cuft you need 15 lbs, or 6 more lbs for the same 30K of capacity. Plus, you never want to use all the capacity or you have to use 15 lbs per cuft to get all the resin regenerated again. It's like waiting to buy gas until you run out, it is not good to do that and can cause engine damage.

Can you tell me how you got .75 ft out of what I said about SFR?

Let's say you have 2 showers running (5gpm) and a toilet is flushed (1.5gpm) and someone starts the laundry washer (3.5gpm), your peak demand is the total of whatever is running so 10 gpm in my example. You would overrun the 1.0 cuft 9 gpm and not get all the hardness out of the water. And I'd be telling you that you should have bought a 1.5 cuft (12 gpm SFR) and set the capacity to the same as the 1.0 cuft and the salt to whatever lbs at 3333 grains per lb.. 2*60gals/day/person= 120* 8= 960* 8 days = 8640 rounded to 9K. That would be 1125 gals minus one day of 120 gals for the reserve with a meter setting of 1000 gals. 9000/ 3333= 3 lbs of salt per regeneration and that gets you a regeneration on average every 8 days with a constant SFR of 12 gpm. Then if you have a child, redo the math with 3 people at 60 gals per person etc..

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Sorry - I am learning, I thought you originally meant that the 1 cu ft was overkill. But it sounds as if I may be better using 1.5 cu ft of resin, and set the capacity setting to 1 cu ft, and the meter to 1000 gal? Of course, that assumes the numbers for the SFR are correct - I'll need to measure those once we move in (closing soon!). I appreciate your help!

The gpm figures I used are real figures. All softeners have an adjustable capacity. You adjust it by the number of lbs of salt used per regeneration. And all softeners allow changing the salt dose/lbs but some manuals do not tell the customer how to adjust the salt dose.

Now if you have twins etc. and at times have the 3 showers running at once plus other water, the 1.5 cuft 12 gpm will be borderline and may be too small.

The gpm figures I used are real figures. All softeners have an adjustable capacity. You adjust it by the number of lbs of salt used per regeneration. And all softeners allow changing the salt dose/lbs but some manuals do not tell the customer how to adjust the salt dose.

Now if you have twins etc. and at times have the 3 showers running at once plus other water, the 1.5 cuft 12 gpm will be borderline and may be too small.

1. OP only has 8 GPG.
2. Most people with 8 GPG don't have a water softener, and they get along fine by using more soap. I lived with 8 GPG of hardness 100% of the time and no softener for years with no real problem. The pipes did not lime up as far as I could tell.
3. If OP passes 2 GPG of hardness through 1% of the time, it is very unlikely that any effects would be noticeable.
4. The odds of having every water load on full at the same time are small.

1. OP only has 8 GPG.
2. Most people with 8 GPG don't have a water softener, and they get along fine by using more soap. I lived with 8 GPG of hardness 100% of the time and no softener for years with no real problem. The pipes did not lime up as far as I could tell.
3. If OP passes 2 GPG of hardness through 1% of the time, it is very unlikely that any effects would be noticeable.
4. The odds of having every water load on full at the same time are small.

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It does not make sense to size for adequate SFR 100% of the time, it is more efficient to cover 99% of use cases. This might be two showers, a toilet and a washing machine. IMO, the 1.5 cu ft size would be a good compromise that will let you use many fixtures without exceeding the softener capacity.

I would only consider the 5600 valve if your water main is 3/4". Any larger and you should use the larger 7000 valve, and of course there is no downside to using the 7000 on a 3/4" supply.

The chances of your unit channeling is slim to none. This would be more of a problem on larger units. Most of the electronic valve thses days have a day override. So if you set the day override for every 7 days, the system will regen if the gallon count has not reached it's max.

That is a lot of pressure drop. The less pressure drop the better. If the price difference is negligible, go for the lowest pressure drop all else being equal.

Edit: The 5600 is equivalent to a 3/4" valve internally despite available adapters. Having suffered through inadequate plumbing in my house I resolved that my new installation would present the least restriction possible. So I chose a pair of 7000SXT and 1" type L copper trunk all the way to the bathrooms. The resulting flow rates vindicated these choices.

1. OP only has 8 GPG.
2. Most people with 8 GPG don't have a water softener, and they get along fine by using more soap. I lived with 8 GPG of hardness 100% of the time and no softener for years with no real problem. The pipes did not lime up as far as I could tell.
3. If OP passes 2 GPG of hardness through 1% of the time, it is very unlikely that any effects would be noticeable.
4. The odds of having every water load on full at the same time are small.

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Yes - I realize that the hardness level isn't that high, but this would definitely help us - we get white stains on the water dispensers from mineral build up. Plus all of the other things as well (etching of the glasses, etc).

Yes - I realize that the hardness level isn't that high, but this would definitely help us - we get white stains on the water dispensers from mineral build up. Plus all of the other things as well (etching of the glasses, etc).

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Agreed. My mother has similar low hardness levels and still experiences the inconveniences of hard water. It is not as bad as my 30 GPG water, but still a maintenance headache.